Effects of elevated CO2 and temperature on photosynthesis and leaf traits of an understory dwarf bamboo in subalpine forest zone, China

The dwarf bamboo (Fargesia rufa Yi), growing understory in subalpine dark coniferous forest, is one of the main foods for giant panda, and it influences the regeneration of subalpine coniferous forests in southwestern China. To investigate the effects of elevated CO2, temperature and their combination, the dwarf bamboo plantlets were exposed to two CO2 regimes (ambient and double ambient CO2 concentration) and two temperatures (ambient and +2.2 degrees C) in growth chambers. Gas exchange, leaf traits and carbohydrates concentration were measured after the 150-day experiment. Elevated CO2 significantly increased the net photosynthetic rate (Anet), intrinsic water-use efficiency (WUEi) and carbon isotope composition (13C) and decreased stomatal conductance (gs) and total chlorophyll concentration based on mass (Chlm) and area (Chla). On the other hand, elevated CO2 decreased specific leaf area (SLA), which was increased by elevated temperature. Elevated CO2 also increased foliar carbon concentration based on mass (Cm) and area (Ca), nitrogen concentration based on area (Na), carbohydrates concentration (i.e. sucrose, sugar, starch and non-structural carbohydrates) and the slope of the AnetNa relationship. However, elevated temperature decreased Cm, Ca and Na. The combination of elevated CO2 and temperature hardly affected SLA, Cm, Ca, Nm, Na, Chlm and Chla. Variables Anet and Na had positive linear relationships in all treatments. Our results showed that photosynthetic acclimation did not occur in dwarf bamboo at elevated CO2 and it could adjust physiology and morphology to enable the capture of more light, to increase WUE and improve nutritional conditions.